The invention relates to a sports shoe with an outer shell of injection moulded plastic, of the type specified in the introductory part of claim 1.
A sports shoe of the generic type, in particular a ski or skate shoe, with a shell of plastic and a comparatively soft inner shoe is known from patent specification EP 0 894 445 A1. In this instance, the shell has at least one region with a rigidity which is lower than the rigidity of the rest of the shell. This region of low rigidity is a relatively flexible region on the external face and/or internal face of the shell and is provided in front of the metatarso-phalangeal joint of a foot when inserted in the shell. Based on a first embodiment, the shell is made from two plastics of differing rigidity and the more rigid plastic is used for the outside of the shell and the flexible region is defined by a cut-out in the rigid plastic, which is closed by a relatively soft plastic in the interior of the shell. These two plastics of differing rigidity or hardness are joined to an integral shell body during a dual injection moulding process. Based on a second embodiment, the flexible region of the sports shoe is again defined by a cut-out in the shell but the inner shoe has a plastic element on its outside which is less rigid than the shell and is disposed so that it closes the cut-out. The flexibility of the region of lower rigidity is selected so that this region is able to deform slightly when placed under pressure by the metatarso-phalangeal joint of the foot, thereby reducing pressure on this foot joint and preventing pain at this point as far as possible. The first embodiment is problematic in terms of the production technology and the degree of elasticity or flexibility which can be obtained is not very satisfactory. The second embodiment is primarily critical in terms of ensuring that the shell is sealed and prevents moisture from getting into the shoe interior.
Patent specification EP 1 571 939 A1 discloses a different design of sports shoe with a relatively rigid shell. In order to increase user comfort, this sports shoe has a plurality of windows or cut-outs in the outer shell, which are disposed on the outside and/or inside of the shoe so that they coincide with the bones and metatarsus. These orifices or cut-outs in the shell are overlapped by cushioning extending from the outer surface of the shell. This cushioning is made up of multi-layered parts made from different plastic materials and is secured to the external surface of the shell so that a sort of sandwich structure is created. A separate part-component of the shoe shell made from a rigid, impact-resistant material defines an externally lying protective plate for the peripheral edge portions of the relatively flexible cushioning element. In particular, the flexible cushioning is partially overlapped by the relatively rigid protective plate and the portion of the cushioning which covers the opening in the shoe shell is left exposed by the protective plate. The flexible cushioning is also attached to the outside of the shoe shell by the protective plate. The protective plate and the flexible cushioning are bigger than the cut-out or opening in the shell by a multiple. In the case of another embodiment, a sealing element made from a water-impermeable material is provided in addition to this sandwich-type cushioning to prevent water from seeping into the shoe or snow from penetrating it. This sealing element is fitted on the external surface of the shell and covers the respective cut-out in the shell. The seal element is in turn overlapped by the cushioning element mentioned above. This previously known design is also relatively complex to manufacture, resulting in high production costs. Furthermore, the compressible cushioning element is exposed to greater risk of damage or breakage at the surface, which may result in problems with regard to preserving the seal of the sports shoe.